The present invention relates to load cells or stain gage sensors in general and in particular to a compression stain sensor in which the sensor is directly compressed by an applied load.
It is known to use load cells and strain gages to sense loads. Conventional load cells typically include a beam and one or more strain gages mounted to the beam. Deflection or bending of the beam due to an applied load changes the shape of the strain gages, resulting in a change in the resistance of the strain gages.
The strain gauges typically consist of thin film or metal foil resistors that are mounted on polyimide films. The film is then mounted to the beam by a gluing process. Generally, a known input voltage is applied to the strain gages and an output signal from the strain gages varies as the resistance of the strain gages vary to provide a signal indicative of the load applied to the load cell.
Other types have load cells use strain gages have used thick film resistors that are mounted to a steel substrate over a dielectric material. As the steel substrate bends or flexes under the applied load, the resistors are placed into tension or compression and the resistance of the resistor's changes.
The load cells of the prior art suffer from a major disadvantage in that their output is influenced by and must be calibrated to the bending substrate. In some applications, the mechanical structure of the device cannot be designed to accommodate a bending beam. Further, the use of glued on strain gages causes variations in the data that is collected due to variations in the strength and thickness of the glue. Therefore, an improved load cell with better accuracy is desired.